The bitter taste of many drugs which are orally administered are disadvantageous in several aspects. For example, the disagreeable taste of drugs causes difficulties in swallowing or causes patients to avoid taking their medication, whereby resulting in low compliance of patients. Thus, taste-masking technologies are considered very important, and are being developed by many researchers. The taste-masking is usually achieved by forming a taste-masking layer on a particle having an active ingredient. However, the taste-masking layer may cause poor drug release profiles. Thus, the formulation design is difficult to provide oral dosage forms having good taste-masking properties and good drug release properties.
European Patent Application No. EP 0409254 discloses rapid-releasing oral particle pharmaceutical preparation with unpleasant taste masked. The oral particle pharmaceutical preparation comprises a core and a film layer coating the core, the core at least containing a drug having an unpleasant taste and a water-swelling agent, and the film layer at least containing ethylcellulose and a water-soluble substance. However, this technology usually requires the heating of final product (e.g., at 60-75.degree. C., 10-20 hr) to attain good drug release properties. The heating treatment is not preferable for heat-sensitive drugs which may be decomposed or melt at such high temperature. Further, in this technology, the effective masking time is described as more than 20 seconds. Such time period is not enough to provide complete masking effect for some patinets such as those with artificial teeth. Also, the previous technology cannot avoid the use of acetone and chlorine solvent (e.g., methyene chloride), which is harmful to human bodies, to provide the sufficient masking effect.
Japanese Patent Application Laid-Open Publication No. S63-258809 discloses fine granules prepared by forming 1 to 10 wt. % of an outer layer on a core particle having a bitter active ingredient, and forming 3 to 10 wt. % of a saliva-insoluble layer on the outer layer. However, this technology cannot provide fine granules having rapid release properties in neutral and alkalic pH media. This is because the polymer composed of the outer layer has solubility strongly dependent on pH in media, and cannot be dissolved and disrupted in the neutral and alkalic pH media.
Accordingly, it would be desired if oral dosage form having improved drug release properties and taste-masking properties were provided.